Radiators have been generally employed for cooling heat generating elements, such as electronic components, internal combustion mechanisms and vacuum pumps. Among several types of the radiators, heat pipe radiators have been well known because of their high heat transfer performance. General heat pipe radiator is constructed mainly from a base plate on which the heat generating element is mounted, and a heat pipe of which a part (a heat receiving portion) is mounted on the base plate. The heat pipe has a sealed space inside of a hollow body which is vacuumed and then charged with a working fluid, such as water, butane and alcohol. Heat transferred to the base plate from the heat generating element is transferred to the heat receiving portion of the heat pipe which is contacted to the base plate, and then causes the working fluid in the pipe to be evaporated. The generated vapor is moved to a portion (a heat radiating portion) of the heat pipe on which the base plate is not mounted, and at that portion, the vapor radiates heat to be condensed to liquid. This phase change and the circulation of the working fluid in the sealed space cause the heat produced by the heat generating element to be dispersed. At the heat radiating portion, a fin may be attached to diffuse the heat efficiently.
As one type of the heat pipes, there is a meandering capillary tube heat pipe, in which a heat pipe is disposed to meander between a heat receiving portion and a heat radiating portion. The meandering capillary tube heat pipe is very useful because of its excellent heat transfer capacity. Such meandering capillary tube heat pipe is disclosed, for instance, in Japanese Laid-open Patent Publication No. Hei 4 (1992)-190090.
FIG. 11 is a partially cross sectional plan view showing a structure of a meandering capillary tube heat pipe disclosed in Japanese Laid-open Patent Publication No. Hei 4 (1992)-190090. The heat pipe 100 has the following characteristics.    (A) The both terminals of the capillary is connected each other so that the capillary is sealed off from the outside (closed loop type).    (B) One part of the capillary acts as a heat receiving portion H, and another part acts as a heat radiating portion C.    (C) The heat receiving portion H and the heat radiating portion C are alternately arranged, and between them the capillary meanders.    (D) In the capillary, a two-phase condensable fluid (working fluid) 101 is sealed.    (E) The capillary has a diameter less than a maximum diameter which allows the working fluid 101 to circulate or move in the capillary while being sealed the inside of the capillary.
A circulating flow of the working fluid 101 occurs in the heat pipe 100, and heat (hot heat) is transferred from the heat receiving portion to the heat radiating portion. The direction to which the working fluid flows depends on the attitude of the heat pipe 100.
When the heat pipe is horizontally arranged, vapor bubbles 103 generated at the heat receiving portion H are compressed at the heat radiation portion C so that the working fluid 101 flows to the heat radiating portion C closest to the heat receiving portion H, thus the working fluid 101 circulates in the arrow direction shown by the solid line in the figure. On the other hand, when the heat pipe is vertically arranged in the bottom heat mode, vapor bubble 103 generated at the heat receiving portion H move up through a connecting portion 105 in which a flow-resistance is the most smallest while the working fluid made by condensing the most of vapor bubbles 103 moves down in the meandering portion by gravity, whereby the working fluid 101 is circulated in the arrow direction shown by the broken line in the figure. On the other hand, in the case for transferring cold heat from a heat receiving portion to a heat radiating portion, the working fluid is condensed at the heat receiving portion and evaporated at the heat radiating portion by reverse manner of the above-described phenomena.
As for the heat transfer characteristic of such closed loop type meandering capillary tube heat pipe, it is found that the heat pipe, in which a liquid (R141b) having a small viscosity coefficient is employed, can exhibit an enough heat transfer capacity even if the inner diameter of the capillary is decreased to 0.8 mm. (Refer to, for instance, “Heat Transport Characteristics of SEMOS Heat Pipe”, Nagata, Nishio, Shirakashi, Baba, The proceedings of the 38th National Heat Transfer Symposium of Japan, (May 2001)). And, as for a initial vacuum at the manufacturing stage of the heat pipe, while a wick type heat pipe requires a high initial vacuum of about 0.010 mm Hg, the closed loop type meandering capillary tube heat pipe exhibits a sufficient heat transfer capacity in spite of requiring a low initial vacuum of about 60 mm Hg.
Also, according to the above reference, how the circulating flow is generated is examined by visualizing the motion of the vapor phase and the liquid phase of the working fluid. As the result, in the closed loop type heat pipe having two pairs of going and returning passages, three main vapor plugs and three main liquid plugs are alternately formed in the heat pipe, and growing and condensing these plugs associated with heating and cooling provides a power for generating the circulating flow between the heat receiving portion and the heat radiating portion.
The heat pipe is also applied for cold heat transportation (a cooling apparatus). In this case, a cold heat generator is attached to the heat receiving portion of the heat pipe, and then cold heat produced from the cold heat generator is transferred to the heat receiving portion of the heat pipe, and to the heat radiating portion through the heat transfer portion to be finally radiated. Here, when an object to be cooled is attached to the heat radiating portion, the cold heat produced from the cold heat generator is transferred to the object through the heat pipe, and cools the object.
By the way, earlier studies has not proposed the constitution of the apparatus when the meandering capillary tube heat pipe is used under a condition in which a heat receiving portion is separated apart from a heat radiating portion, and an enough space for connecting the both portions does not exist. And, the above Nagata's paper describes that a heat transfer is easily carried out by generating a moving power for a circulating flow in the case of a closed loop type heat pipe having two pairs of going and returning passages. However, it does not describe the case of a closed loop type heat pipe having one pair of going and returning passages.